As environmental destruction or exhaustion of resources becomes an issue, an interest in a system capable of storing electric power and efficiently utilizing the stored electric power is increasing. In addition, importance on renewable energy such as photovoltaic generation gradually increases. In particular, studies on applicability of renewable energy are being made in a variety of fields because it uses natural resources such as solar power, wind power, or tidal power that are supplied infinitely and does not generate pollution in the course of generation.
In general, in the field of the renewable energy system, a new energy source has been studied and developed, or conventional fossil energy has been converted efficiently in order to address problems such as an energy crunch or environmental pollution. For example, energy can be obtained by converting regenerable energy such as solar power, water power, terrestrial heat, and biological organisms or future energy sources for supplying sustainable energy. As such a renewable energy system, there are known a wind power system, a photovoltaic generation system, and the like.
According to the Korean reliability criteria, the power grid system is required to maintain a frequency of 60±0.2 Hz. Such a power grid system enforces a frequency control ancillary service for a frequency control pursuant to the reliability criteria. The frequency control ancillary service includes a frequency response ancillary service and a frequency regulation ancillary service, and there are also markets for each service. Therefore, generation resources are required to participate in the frequency response market or the frequency regulation market to provide the frequency control ancillary service.
An electricity market consists of a day-ahead market and a real-time market. The day-ahead market is a market opened one day ahead of operation, and the real-time market is a market opened additionally for unexpected reasons such as a system situation of the operation day. If a large-capacity battery bids for the frequency regulation market and conducts frequency regulation, it can guarantee high reliability with a fast response speed, and can provide fixed output power and maximum output power to conventional power generators whose output power is fluctuating in a power grid system. However, due to a capacity restriction in the large-capacity battery, the large-capacity battery is restricted in participation in the frequency regulation market.
As one of the battery charge/discharge techniques of the prior art, a technique of estimating a contract price in the electricity market has been proposed. Specifically, in this technique of the prior art, in order to increase a successful bidding possibility, a contractible price is predicted by checking a reserve margin of the electricity market or a history of the contract price, and this predicted price is applied to a bid.
However, this technique of the prior art merely focuses on a technique relating to a successful bid of the battery based on the contract price history and fails to discuss a battery operation method after the contract.
In addition, in state-of-charge (SOC) management of the battery, an optimum charging time is calculated on the basis of a result of the bidding for electricity generation in the distributor's side. Therefore, when a battery is used as a frequency regulation reserve whose signal changes in a real-timely manner, the battery SOC continuously decreases or increases, so that it may exceed a battery charge/discharge allowance level disadvantageously. Therefore, there is a demand for a system capable of more effectively and economically operating a battery and stably managing a battery SOC when the battery is used as a frequency regulation reserve.